The Prophecy of The Stones by Flavia Bujor

also known as: The Prophecy of the Gems

Jade, Opal and Amber are three totally different girls.
Jade is rich living with her father, spends half her time daydreaming, and the other half landed in reality.
Opal is living in with her aunts in a normal town, with everyday-life destroying her fantasy.
Amber is poor living with her sick mother, with her mind never in the real life, always dreaming.
They all have the same birth day, and when they turn 14 their parents tell them they are adopted and give them their birth stones. After that they are send to meet each other, with the warning that they are enemies, and the destination of a magical kingdom, to learn about their prophecy and stop the Council of Twelve.
With their story we also learn the one of Joa, a sick girl in the hospital. The girls are actually in her dreams.
The book has a fast, interesting plot and intoduces us to a magical world where the laws of nature don't apply. The main subject is hope, that people can change everything, even fate, as long as the have faith.